Why carry out this study?

Fixed-combination therapies could simplify treatment regimens and additionally avoid diluting and/or washing each drug by non-interval administration of single drugs concomitantly.

Drug pharmacokinetics of fixed-combination ophthalmic solution would be affected by their formulation composition and drug-drug interaction, but the knowledge of these points is limited.

We tried to clarify and compare the pharmacokinetic profiles of the new fixed-combination ophthalmic solution of 0.1% brimonidine tartrate and 0.5% timolol with that of the respective single drugs alone and/or concomitantly.

What was learned from the study?

Ocular and systemic pharmacokinetics of brimonidine were comparable among fixed-combination, single drug and concomitant administration, but those of timolol were differ among these groups.

The present study suggested the difference of pharmacokinetics in timolol is caused by the pharmacologic action of brimonidine but not by formulation composition, providing an information in pharmacokinetics under fixed-combination therapies.